The present invention relates to compressors and, in particular, to compressors which have reciprocating pistons carried by an eccentrically rotating member. Such compressors are supplied as components to original equipment manufacturers for use in a wide variety of applications, ranging from spraying equipments to pneumatic tool operation.
In some applications, the precise output of the compressor may be critical. In such situations, it is desirable to be able to adjust or fine tune the compression ratio of the compressor. When used herein, the compression ratio is the ratio of the volume above the piston at the bottom of a stroke to the volume above the piston at the top of a stroke. Therefore, even though the size of a stroke will remain constant with a given eccentric, the output, or compression ratio, can be modified by changing the length of the piston rod. As clearance above the piston at the top of the stroke is reduced by making the rod longer, the compression ratio increases.
In some compressors, there is a need to maximize the compression ratio. In other instances, the optimal compression ratio may be one other than the maximum. In other instances, rod material or assembly considerations, variations in dimensional tolerance may make it impossible to precisely achieve a desired rod length. It is also important to provide adjustability of the piston rod length without extensive or complex operations requiring skilled labor.
Another important factor in compressor performance is the durability of a piston's seal. Depending upon the frictional characteristics or other properties of a seal, continuous or intermittent usage may cause early failure of the seal, even though the other working parts of the compressor may be far from failure. In such cases, replacement of the seal may be desirable. In many compressors, replacement of piston rings or seals is a major undertaking which requires significant time and skilled labor.
It is therefore an object of the invention to provide a compressor in which the piston rod length can be adjusted.
It is a further object of the invention to provide a compressor in which the piston rod length can be changed without extensive disassembly of the compressor which may require skilled labor.
Yet another object of the invention is to provide a compressor in which adjustment of the piston rod length can be achieved quickly and precisely.
Still another object of the invention is to provide a compressor in which the piston seal or ring can be replaced without removing the piston and rod assembly from the compressor.
Yet another object of the invention is to provide a compressor in which both replacement of the piston seal and adjustment of the piston rod length can be achieved with a minimum of complexity and labor.
These and other objects of the invention are achieved with a compressor which includes a housing and a motor driven eccentric onto which is mounted a lower rod piston section. The lower piston section is attached to a main piston section which carries a seal clamp. Fasteners are used to hold a seal between the seal clamp and the main piston section. Other fasteners are used to allow shims to be placed between the lower end of the main piston section and an upper surface of the lower piston rod section to affect a change in the output of the compressor. Both replacement of the seal and adjustment of the piston rod length can be achieved by simply removing the compressor heads and without requiring access to the connection between the lower piston rod and the shaft.